Hydraulically operated machine tool



May 6, 1941. l-:..J`. HlRvNE-N HYDRAULICALLY OPERTED MACHINE TOOL ,piled sept. faz; 195s f2 Sheets-Sheet 1 May es,` 1941.

E J. HlRvoNEN HYDRAUL-IGALLY OPERATED MACHINE TOOL Fuga sept; 2z, 19:59

2f sheets-sheet 2 www i produced thereby.

, PatentedMay 6, 1941 I UNITED STAT Es', PATBNT oFFlcE mnemonic? emanan Eric '1.- 'Hirvone-n, .Worcester, fa'lslgnor to Leland-Gifford Company, Worcester-.Mash a corporation ofMassachu'letts I Application september sz, i939, serial No. 296,982V a z claims., (or 'zr- 1) This invention7relates to hydraulically opergrinding machines and the like, especially charat'ed machine tools, such 'as boring machines,

acterized by the extreme accuracy of the work When a machine tool of the above type isin- 4tended to produce work, and especially duplicate pieces, accurate within one ten thousandths part 4of an inch extreme care must be paid not onlyto the initial manufacture of the machine but 'even to the cutting tool for it is apparent that if the cutting tool does not produce a surface smooth enough to measure within a ten thousandths the finer accuracy inherent in the machine is not evidenti@l Furthermore, it is neces.-

Asary not only to provide,- this accuracy initially but to maintain it throughout a succession oi duplicate work pieces and indefinitely.

A hydraulically operated machine tool has a base on which is mounted a cutting toolrholder and a work support, one of which is movable relatively to the other by a hydraulic motor, usually` a cylinder and a piston therein. The motor is `supplied with operating fluid, usually oil, by'a motor driven pump` such asa gear or'other constant displacement pump that takes oil from -a `storage tank and delivers it under suitable pressure under control by appropriate valve mechanism to the motor. The machine base is come monly hollow and it is common to utilize the base causes them to expand with an increase of tem` perature and to contract with a'decrease of temperature. Thus the" dimensions of the base undergo frequent changes of dimensions which is not conducive to` maintenance of working accuracy. For instance.A an increase in temperature or only ten degrees centigrade will expanda linear inch oi' cast iron, of which the machine bases arev commonly made, more than the desired machine .accuracy and, since the bases have sizable dimensions it can be appreciated that f a small change of temperature can produce a relatively great change of dimensions. Furthermore,

' the diilerentparts of the base have diierent thicknesses or have different masses attached This heat is transmitted by direct heated vand cooled unequally. yThus, the effect of the heated oil is to throwv the operative parts of the machine out of their intended relation and impair the accuracy of the work produced by the machine. The errors introduced by the temperature'of the oil may be aggravated in a machine" that is 'started and stopped frequently for loading and unloading the workand where during the idle periods the machine tends to cool so that successive work pieces lare not machined to the .same degree ci accuracy. l l

` It is an object of the prese'nt invention to eliminatev the'` above enumerated troubles dueto oil temperatures by storing the oil in the base of the machine in a 'reservoir or tank that is structurally separate from the base and thermally insulated therefrom so that variations of oil temperatures have ane'gligible influence on `the machine accuracy, and further to provide for the ventilation of the base an the circulation of air between the -oil reservoir and the walls of the base to assist in maintaining an unvariable base temperature.

Another object is generally to improve the construction and operation of hydraulically operated machine tools.

I Fig. 1 is a front elevation, partly in section. of a hydraulically operated boring machine embodying the invention.-

Fig. -2 is an'end elevation of the machine of Fig. 1.

Fig. 3 is a section taken along line 3-3 of Fig. 1. l

Fig. 4 is a section taken along line l-l of Fig. 3.

'Ihe hydraulically operated machine tool herein chosen for illustrating the invention is a boring machine oi!A extreme accuracy, producing work accurate to one ten thousandth part of an inch.

The boring machine comprises a base I0 upon one end of which is mounted a spindle housing I-2 containing a spindle Il driving `a cutting tool I6.

'I'he top part of the base is provided with ways I8 on .which a carriage 20 is reciprocable in the line of and toward -and away from the spindle. The carriage supports a suitable ilxture 22 for engaging and supporting the work tobe operated on by the tool or cutter I0.

The carriage 20 is reciprocated hydraulically by a hydraulic motor including a cylinder 24 xed to the top part of the base, under the carriage;

and having a piston therein the piston rod 28 thereto so that different'parts of the machine are of which extends through one end of the cylinder and at its end part has a iixed driving connection 3l with the carriage.

The base I0 ofthe machine -is hollow and its four vertical walls l2, 3l, 36, 38 enclose a com? partment 40 that is closed at the top part and substantially open at the .bottom part except where the bottom part is traversed by the medial longitudinal rib e2 and the wide transverse rib Iland the narrow transverse rib 46. `The end walls u .and 38 have large openings therein. provided with removable cover plates dlandl respectively formed with louvres 52 through which the compartment d@ is ventilated.

In accordance with this invention the oil tank V or reservoir 5t is separate from the machine base and is located within the base, supported upon the aforesaid ribs 42, M, and 48 through interor blocks 56. Thus the bottom wall 58 of the tank is supported out of heat transferring relation with said ribs. 'Ihe vertical side walls 8B, l2, il, 66`of the tank are substantially spaced from the associated confronting walls 32,' 34, 8B,-

. posed, heat insulating relatively thick cork pads 15.

and 44 and pass through clips 12 that bear on the cover. ,The tie rods are long so that heat transference therethrough is negligible.

The hydraulic system also includes a pump and spindle driving and control unit mounted on the ytank cover within the base. Said unit includes a driving electric motor 'Il which drives a unitary mechanism including an oil` pump 'I8 of the constant displacement gear type and va. clutch and brake mechanism 'I8 which controls the ro` tation of a drive shaft 8 0 that driv the spindle Il through belts 82 and 8l. The oil pumpeis rotated continuously with the motor 14 while the spindle i4 can rotate ox' be held stationary lby the clutch and brake mechanism 'Il the construction of which is not herein essential to an understanding of the present inventiomf The oil pump 'Il takes oil from the tank Il and not herein necessarily illustrated from whence the pressure oil passes under controiof a valve mechanism generally indicated at I6 to the table reciprocating cylinder 24, the exhaust oil returning to the tank. As set forth above the oil becomes heated which raises the temperature of the tank. Since, however, the tank is thermally insulated from the machine base 'by the arrangement herein described, the base is not deleteriously iniiiuenced by the oil temperature and hence the machine accuracy is preserved.

I claim:

l.. A hydraulically .operated machine tool of the type carrying a self-contained internal reservoir, comprising a base, cutter and work holders thereon, a hydraulic motor for effecting relative movement between said holders, said base having a Vhollow lower part formed with side walls and with bottom members traversing the lower part of' said hollowpart and being rigidwith certain of said side walls, an oil tank mounted upon said 'bottom memberswithln said hollow part and means rigidly securing said tank in the aforesaid relation to said bottom members. Y

2. A hydraulically operated machine tool as in claim 1, said means rigidly securing said tank to said bottom members comprising bolts which alje connected to the top part of the tank andto said bottom members 'and are long to minimize' the tank to.y

heat conduction therethrough from said bottom members.

ERIC J. amvoNEN. -l 

